The grandson of Lord of the Rings author J.R.R. Tolkien has inked a whopping six-figure book deal on the eve of the premiere of The Lord of the Rings movie.

But Simon Tolkien insists he's not a shameless opportunist merely trying to cash in on his granddad's renewed fame. 

"I would never write a fantasy book. What I am doing in fiction bears no relation to J.R.R. Tolkien," said Simon, a 42-year-old British lawyer. 

"I've found it quite difficult being [his] grandson. People see you as important simply because you are related to someone else." 

Simon has penned The Stepmother, a novel he calls a "psychological mystery" aimed at the American mass market. 

"I like to write books that keep people turning the pages. I think I've got a talent for dialogue and a lot of expertise of what happens in the courtroom, which is very useful for this kind of book," he said. 

The tome, to be published by Random House, concerns the teen son of a politician who suspects his father's second wife may have conspired to murder his mom. 

The novel comes 28 years after the death of Tolkien's grandfather and as the film version of The Lord of the Rings: Fellowship of the Ring makes its debut. 

The PG-13 flick, starring Elijah Wood, Ian Holm and Liv Tyler, opens Wednesday and has received advance praise from critics who say it's better than Harry Potter and the Sorcerer's Stone

The first of three Rings movies, which together cost $275 million, it chronicles the epic battle between the young hero hobbit Frodo and the Dark Lord Sauron, who wants to enslave the people of Middle Earth. 

Simon Tolkien said his grandfather's multimillion-selling trilogy had been an inspiration to him as a child, but added his own literary goals were different. 

His work has much more in common with legal-thriller writer John Grisham than elves and fairies, he said. 

"I don't see the film as a threat to the book, but as something extra. As a result of this film, because it's good, more people will want to read the books."

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